The present invention relates to a process for obtaining sorbitol and gluconic acid, or gluconate, by fermentation in the presence of permeabilized Zymomonas mobilis cells, starting from aqueous glucose/fructose mixtures, and to a permeabilized cell material suitable for this purpose.
It is known that sorbitol and gluconic acid, or gluconate, are formed enzymatically in aqueous glucose/fructose mixtures with the aid of glucose dehydrogenase and sorbitol dehydrogenase in the simultaneous presence of cofactors. A prerequisite of this process is the continuous addition or regeneration of the cofactors.
A process has therefore been developed (U.S. Pat. No. 4,755,467) for the microbial conversion of glucose and fructose in aqueous solution with the aid of bacteria containing glucose/fructose transhydrogenase, in particular of Zymomonas mobilis. In this process demineralized cell-free extracts, or immobilized cells, or non-growing cells washed with phosphate-free buffer are used which may have been rendered permeable, for which purpose a toluene treatment was exemplified. An alternative object is the formation and application of gluconate kinase-negative mutants.